hmm… the drawing i’m working on right now with that same computer and the latest beta release (501) is preforming very nicely. (though it’s not 65MB… it’s at 8MB so far)…
are you experiencing ‘freezing’ on other files as well or just this one in particular? if it’s only this file, you should probably send it to mcneel via:
there was a person here the other day with a similar sounding problem as yours but it turns out, they had a misbehaving object in the file… see this thread: